A conventional cold cathode fluorescent flat lamp (CCFFL) comprises several UV lamps with fluorescent powder coated on inner walls thereof. A high voltage is applied across the electrodes thereof to generate UV lights, which illuminate the fluorescent powder to form visible lights. In a CCFFL disclosed in R.O.C. Pat. No. 495,796, after a chamber is vacuumed, noble gas and mercury vapor are filled therein, and a high voltage is then applied across the cathode and anode thereof through a circuit board to generate UV lights, which illuminate fluorescent powder coated on the inner wall of the chamber to form visible lights. However, because of residual organic solvent, the situation of burned black will occur at the electrodes of the CCFFL after a longtime use, hence seriously affecting the light emission efficiency. Therefore, how to manufacture a flat lamp, which can be used for a long time without affecting the light emission efficiency becomes a problem to be solved urgently by the display and lamp industry.